JPS6032444A - Data transmission system by light - Google Patents

Abstract

PURPOSE:To simplify the constitution of the data transmission system by frequency-modulating the light of lighting fluorescent light by data and transmitting the transmission data in the form of the light from the fluorescent light to eliminate the light source for optical transmission. CONSTITUTION:A digital signal (a) from a transmission signal generator T is received by a modulator M, where a signal corresponding to the transmitted data is frequency-modulated and an FM modulation signal (b) is outputted. The signal (b) drives the lighting fluorescent light F and the light from the fluorescent light F driven through the FM modulation is received by a receiver R. The light signal is converted into an electric signal by a pin photodiode P of the receiver R, amplified by an amplifier A and fed to a demodulator D. The demodulator D demodulates the data signal from the FM modulation wave, waveform-shaped by a waveform shaping circuit S and a digital output signal (c) is fed to a central processing unit CPU. Then the constitution of the data transmission system by using light is simplified.

Description

[Detailed Description of the Invention] (Technical Field) The present invention relates to a data transmission system using light.〇 (Prior art) As a data transmission system within a building, etc., light modulated with data is transmitted throughout the building. A system is being considered in which the optical transmission data can be received at any desired location within a building by filling the building with the optical fiber.

In order to generate such transmitted light, for example, a plurality of light emitting diodes (LlmD) are used, and the wavelength of the transmitted light is often in the infrared region. The reason for this is that infrared light has a low attenuation rate when reflected from walls, so there is a high possibility that the light will reach a long distance.

However, when using such LED '& -LE
Since the optical output of D is small, the receiving device must be highly sensitive, and since the optical output is small, e Lg
D light sources need to be scattered throughout the building,
A dedicated drive device for this purpose must be placed at the location where the LED light source is installed - increasing the installation cost. In addition, when using an infrared LED, it is not possible to easily visually confirm whether or not the emitted light is incident on the light receiving section. (Objective) Therefore, the object of the present invention is to remove shortcomings.

An object of the present invention is to provide an optical data transmission system that can appropriately transmit data within a premises by modulating a phantom driving waveform without adversely affecting the original illumination. be.

By using the fluorescent light for illumination in a building as well as for data transmission, there is no need to place special light-emitting devices in various places in the building, and moreover, it is possible to supply light with higher luminous power to the receiver. can. Moreover, it also uses infrared LEDs1
However, in the present invention, the receiver cannot know whether or not the transmitted light is actually incident on the light receiving section.
You can be confident that you can receive reception anywhere where the fluorescent lights are on and there is bright light.

(Example) The present invention will be described in detail below with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the optical data transmission system of the present invention.

Here, T is a transmission signal generator that generates a digital signal a corresponding to data. M is a transmission signal generator T
This is a modulator that receives a digital signal a generated from a FM modulator and changes the output frequency corresponding to the reception, for example in the form of FM modulation, thereby obtaining a signal for driving a fluorescent lamp. In this modulator M.

For example, the frequency V when the digital signal a is ff1+1 is set to be higher than the frequency when the digital signal a is "0". In this way, the output signal b from the modulator M
It will look like the waveform in Figure 2.

F is a fluorescent lamp, which is driven by the driving signal of the modulator M. + and generates fluorescence. The intensity of the light output under this fluorescent moon is constant, but the light emission frequency changes depending on the driving signal. R is a receiver that receives light from the fluorescent lamp F and restores the original data.

FIG. 2 shows the waveform of the digital signal a outputted from one transmission signal generator T and the waveform of the fluorescent lamp driving FM modulation signal 1 outputted from the modulator M in correspondence with each other.

FIG. 3 is a block diagram showing one embodiment of the receiver R.

Here, P is a pin photodiode that receives light from the fluorescent moonlight and converts it into an electrical signal, and A is a pin photodiode P.
An amplifier that receives the output from the amplifier A, extracts and amplifies only the signal near the transmission frequency from that output, and D receives the amplified signal by the amplifier A and amplifies the modulated signal. It is a demodulator. Scenes from shat e-choki■]
This is a waveform shaping circuit that receives the A signal and converts it into a digital signal 6.

The CPU is a central processing unit that receives the digital output signal C from the waveform shaping circuit S and executes various calculations.

As you can see from the above explanation, the amplifier A and demodulator operate in the same way as a conventional FM receiver.
A digital signal C1 having a waveform shown in FIG. 2, that is, a signal corresponding to the original digital signal a, is obtained from the A/D conversion circuit S.

As described above, in the present invention, the waveform for driving the fluorescent lamp is
The original data is transmitted after M modulation. The reason for this is that by driving the fluorescent lamp using the -FM modulation method, the intensity of the light does not appear in the output light of the fluorescent lamp F as in the case of -AM modulation. Also, by using such a modulation method.

There is an advantage that reception can be performed with less noise even in places where the received light signal is weak. There is no need to provide a special light source device for optical transmission (and the cost of installing an optical data transmission system can be reduced).

Also, since it uses fluorescent light for illumination, there is no shortage of output optical power unlike with LEDs, and there is no need to install light sources in various places just for optical transmission, from this point of view. Contributes to reducing the installation cost of optical transmission systems.

Furthermore, since the present invention uses fluorescent light for illumination, data transmission is always possible while the light is on.

There is no need to provide any special means to confirm whether or not the light source is being driven.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention. FIG. 2 is a signal waveform diagram of the transmission signal and the fluorescence (J drive signal and reception signal). FIG. 3 is a block diagram showing a specific example of the receiving section shown in FIG. 1. A... Amplifier - D... Demodulator. F... Fluorescent light. M... Modulator. P... Pin photodiode - R... Receiver. S... Waveform shaping circuit. T... Transmission Signal generator. CPU...Central processing unit. Figure 1 Figure 3 Figure 21'32

Claims (1)

[Scope of Claims] 1) An optical data transmission system characterized by modulating fluorescent light for illumination with data and transmitting the data in the form of light from the fluorescent lamp. 2. An optical data transmission system according to claim 1, characterized in that the modulation is an FM modulation system. Margin below C)